In order to maintain the green color associated with vegetables, strict attention must be paid to the chlorophyll molecule which is responsible for said green color. The presence of an acid environment causes the breakdown of the chlorophyll molecule, hence, the loss of green color. Although most green plant tissues are naturally quite acidic, chlorophyll is bound to lipoproteins which in some way protect it from the acid. During thermal processing, the protein which protects the chlorophyll coagulates exposing the chlorophyll to the adverse effect of the acid.
Numerous attempts have been made to protect the chlorophyll, such as neutralizing a portion of the acid and thus raising the pH of the plant tissue in question by the addition of an alkali. For instance, U.S. Pat. No. 1,201,666 by Werner teaches that the addition of small quantities of an alkaline substance to green vegetables prevents the impairment or destruction of the greenish tinge associated therewith.
Also, U.S. Pat. No. 2,390,468 by Shroder et al. describes a treatment of green vegetables by cooling them immediately after blanching and applying a slightly alkaline solution to the vegetables for a time, then packaging said vegetables in a slightly alkaline solution of magnesium carbonate. Other references such as U.S. Pat. No. 2,520,214 by Kenworthy Jr., U.S. Pat. No. 2,186,003 by Blair and U.S. Pat. No. 2,189,774 also by Blair disclose the treatment of vegetables at different intervals in their processing with an alkaline solution.
The above references are concerned more with the treatment of green vegetables with an alkaline solution and less with the removal of oxygen from the surface of the green vegetables which further degrades the chlorophyll during low temperature, refrigeration storage. In the present invention the surface micro air layer is removed and replaced with de-aerated water.
It is, therefore, the object of the present invention to preserve the green color of blanched vegetables.
A further object of the present invention is a process for preserving the green color of blanched vegetables stored at refrigeration conditions for extended periods of time.